Tissue-specific chromosomal non-histone protein interactions with DNA.

A group of chromosomal non-histone proteins with affinity for DNA (NP) was isolated from rat liver and Novikoff hepatoma. This fraction, which represents less than 5% of the total chromatin protein content, binds preferentially to unique, double-stranded sequences of fractionated homologous DNA. The interactions are strong at low ionic strength (Km = 6.7 X 10(-9) M) and decrease with rising salt concentration. Complexes of the NP protein fraction with homologous DNA are immunologically tissue-specific. As determined by microcomplement fixation, the NP proteins in Novikoff hepatoma are associated with the transcriptionally active, diffuse fraction of chromatin.